1. Field of the Invention
The present invention relates to a determination of the closed position of a throttle valve of a vehicle internal combustion engine using accelerator pedal position information.
2. Description of Related Art
Certain vehicle internal combustion engines equipped with an electronic throttle body rely on a powertrain control system (PCS) to process the vehicle driver""s demanded accelerator pedal position as one of several inputs to demand and control power from the engine by control of airflow through the throttle body. The PCS calculates the driver demand by taking the difference between the current accelerator pedal position and a closed accelerator pedal position corresponding to a closed throttle valve that in turn corresponds to an engine idling condition.
An incorrect determination of a foot-off accelerator pedal position (i.e. forcing an incorrect throttle valve position) thus can result in the PCS""s commanding an incorrect airflow. For example, an incorrect determination of the closed throttle valve position can occur when the accelerator pedal snaps back after the driver abruptly removes his foot; for example, when the driver""s foot slips off pedal. In this situation, the accelerator pedal returns temporarily to an abnormal pedal position outside the expected normal range of foot-off pedal positions such that a determination of such a xe2x80x9csnap-backxe2x80x9d pedal position will result in an incorrect airflow control command by the PCS. In addition, incorrect determination can occur when a reverse load is applied to the accelerator pedal when, for example, the driver""s foot pulls upwardly on the front of the pedal such that the pedal is temporarily at an xe2x80x9cpull-backxe2x80x9d pedal position outside the expected normal foot-off pedal position range. A determination of such an abnormal xe2x80x9cpull-backxe2x80x9d pedal position in this situation also will result in an incorrect airflow control command by the PCS.
The present invention provides pursuant to one embodiment a method and control system for determining a closed throttle position of a vehicle internal combustion engine using signal values representative of a foot-off position of an accelerator pedal. The invention involves storing a plurality of signal values representative of previous foot-off positions of the accelerator pedal typical of a normal range of pedal positions, determining an average of these signal values, determining a current foot-off position value of the accelerator pedal, comparing the current foot-off pedal position value and the average, and using the average to determine a closed throttle position when the comparison is indicative of an abnormal pedal position.
In another embodiment of the invention, the current foot-off pedal position value is determined after a predetermined period of time after the pedal has moved to a foot-off pedal position, the time period being selected to avoid making a determination of pedal position when the pedal is in a abnormal xe2x80x9csnap-backxe2x80x9d position.
In a particular embodiment of the invention, an initial signal value representative of an initial foot-off position of the accelerator pedal upon vehicle engine power-up is stored and compared to the current foot-off pedal position value. If an abnormal pedal position is indicated, then the comparison of the current foot-off pedal position value and the average of the previously stored pedal position values is made.
In another particular embodiment of the invention, the current pedal position value is determined as a rolling average of sensed pedal position values over a time period.
The present invention provides pursuant to another embodiment a method and system for determining a foot-off accelerator pedal position embodying features described above.
The present invention is advantageous to improve determination of the foot-off accelerator pedal position and thus the closed throttle valve position during vehicle operation by reducing or avoiding sensing of abnormal pedal positions resulting from temporary xe2x80x9csnap-backxe2x80x9d or xe2x80x9cpull-backxe2x80x9d accelerator pedal events. The present invention thereby improves of control of the throttle valve which in turn controls airflow to the internal combustion engine.
The above advantages of the present invention will become more readily apparent from the following description taken with the following drawings.